Spectral-domain optical coherence tomography (SD-OCT) is a non-contact, non-invasive three-dimensional (3D) imaging technique, which performs optical sectioning at micron resolution. OCT was commercially introduced to ophthalmology in 1996, and is widely used in ophthalmology for identifying the presence of various ocular pathologies and their progression. This technology measures the optical back scattering of the tissues, making it possible to visualize intraocular structures such as the retina and the optic nerve head. The ability to visualize the internal structure of the retina makes it possible to diagnose ocular diseases, such as glaucoma and macular hole, objectively and quantitatively.
Although OCT imaging technology continues to evolve, technology for automated OCT image analysis and interpretation has not kept pace. With OCT data being generated in increasingly larger amounts and captured at increasingly higher sampling rates, there is a strong need for computer assisted analysis to support disease diagnosis and tracking. This need is amplified by the fact that an ophthalmologist making a diagnosis under standard clinical conditions does not have assistance of a specialist in interpreting OCT data. This is in contrast to other medical imaging situations, where a radiologist is usually available.
The macula is located at the center of the retina and is responsible for highly-sensitive, accurate vision. Acute maculopathy can cause the loss of central, sharp vision and even lead to blindness. For example, diabetic retinopathy, one of the leading causes of blindness worldwide, is often associated with macular edema (ME). According to a study conducted in 2004, among an estimated 10.2 million US adults aged 40 and older known to have diabetes mellitus, the estimated prevalence rate for retinopathy was 40.3%. Another type of maculopathy, called age-related macular degeneration (AMD), is the leading cause of visual loss among elderly persons. One study reported that 30% of individuals aged 75 and older have some form of AMD. Another disease that can lead to blindness is called macular hole (MH), which is less common than ME and AMD. The overall prevalence is approximately 3.3 cases in 1000 in those persons older than 55 years. As the size of the elderly population increases in the US and many developed countries, the prevalence of maculopathy has increasingly significant social and economic impact. Thus, the diagnosis and screening of macular disease is important to public health.